JP2011077115A - Aqueous dispersion for chemical mechanical polishing and chemical mechanical polishing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an aqueous dispersion for chemical mechanical polishing and a chemical mechanical polishing method, for polishing a workpiece provided with a wiring layer containing tungsten at a high polishing speed to obtain flatness of high level while suppressing corrosion of a tungsten film surface. <P>SOLUTION: The aqueous dispersion for chemical mechanical polishing for polishing the workpiece provided with the wiring layer containing tungsten contains (A) polyethylene imine, (B) persulfate, and (C) colloidal silica, wherein the content of polyethylene imine (A) is 0.002 to 0.28 mass% and the pH is 1-3. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an aqueous dispersion for chemical mechanical polishing and a chemical mechanical polishing method.

  In recent years, with the increase in definition of semiconductor devices, the miniaturization of wiring layers formed in the semiconductor devices has progressed. Along with this, a technique of planarizing the wiring layer by chemical mechanical polishing (hereinafter also referred to as “CMP”) is used. As this technique, for example, after depositing a conductor metal such as aluminum, copper or tungsten in a fine groove or hole provided in an insulating film such as silicon oxide on a semiconductor substrate by a method such as sputtering or plating. A damascene process is generally used in which the excessively laminated metal film is removed by CMP, and the metal is left only in the portions of fine grooves and holes (see, for example, Patent Document 1).

  In particular, tungsten having excellent embedding property is used as a material such as a plug for electrically connecting the wirings in the vertical and vertical directions. (In this specification, wirings, plugs, and the like are collectively referred to as “wiring layers”.)

  In CMP for forming a tungsten plug, a first polishing process for mainly polishing a tungsten layer provided on an insulating film, and a second polishing process for polishing a barrier metal film such as a tungsten plug and titanium, and an insulating film. Are implemented in order. (Note that in this specification, the tungsten layer and the tungsten plug are collectively referred to as a “tungsten film”.)

  Regarding such chemical mechanical polishing of a tungsten film, for example, Patent Document 2 discloses a high polishing rate and a rough surface of the wafer surface after polishing in polishing that corresponds to a stage before finish polishing (corresponding to the first polishing process). Abrasive grains (such as colloidal silica), basic low molecular weight compounds (such as amine compounds), and nitrogen-containing groups for the purpose of preventing this (due to the high reactivity between amine compounds as polishing accelerators and silicon) A semiconductor polishing composition containing a water-soluble polymer compound containing polyethylene (such as polyethyleneimine) is disclosed.

Further, Patent Document 3 discloses a chemical mechanical polishing composition containing a tungsten etchant (such as an oxidizing agent), a tungsten etch inhibitor (such as a specific polymer containing nitrogen atoms) present in an amount of 1 ppm to 1000 ppm, and water. A method for chemical mechanical polishing of a tungsten-containing substrate, which is polished by using the above, is disclosed. The chemical mechanical polishing composition used in this polishing method comprises, as optional components, an abrasive (such as silica, preferably colloidal), and a per compound (monopersulfate (SO ₅ ^2- ), dipersulfate). Salt (S ₂ O ₈ ²⁻ ) and the like).

  However, an aqueous dispersion for polishing a tungsten film that can achieve a higher polishing rate, advanced planarization of the surface to be polished, and suppression of corrosion of the surface to be polished in a balanced manner has not been obtained.

  In Patent Document 4, although not a chemical mechanical polishing aqueous dispersion with the damascene process in mind, an abrasive (silica, etc.), a liquid carrier (water, etc.), a positively charged polymer electrolyte ( A chemical mechanical polishing system is disclosed in which the abrasive is colloidal and stable and includes particles electrostatically bonded to the positively charged polyelectrolyte. For example, in the composition described in Example 1, the content of the polymer electrolyte in the mechanical polishing system is 2.5 wt%.

Special table 2002-518845 gazette JP 2007-19093 A Special table 2008-503875 gazette JP 2005-518091 A

  An object of the present invention is to provide an object to be processed (such as a semiconductor wafer) provided with a wiring layer containing tungsten, particularly a surface to be processed in which an insulating film such as a tungsten film and a silicon oxide film coexists. An object of the present invention is to provide an aqueous dispersion for chemical mechanical polishing and a chemical mechanical polishing method for polishing at a high polishing rate so as to be highly flat and while suppressing corrosion of the tungsten film surface.

The chemical mechanical polishing aqueous dispersion according to the present invention is a chemical mechanical polishing aqueous dispersion for polishing a workpiece provided with a wiring layer containing tungsten,
(A) polyethyleneimine;
(B) persulfate;
(C) containing colloidal silica,
The content ratio (M _A ) of (A) polyethyleneimine is 0.002 to 0.28% by mass,
The pH value is 1-3.

The (B) persulfate may be ammonium persulfate.
The number average molecular weight of the (A) polyethyleneimine may be 200 to 1,000,000.

(B) the content of the persulfate (M _B) may be 0.5 wt% to 3.3 wt%.
Wherein (C) the content of colloidal silica (M _C) may be 1% to 20% by weight.

The object to be processed may be an object to be processed including an insulating film having a tungsten plug.
(A) the content of polyethyleneimine (M _A) [wt%] and the (B) content of the persulfate (M _B) [wt%] _{is, 0.0005 ≦ M A / M B} ≦ 0. There may be five relationships.

  The chemical mechanical polishing method according to the present invention is to polish an object to be processed provided with a wiring layer containing tungsten using the chemical mechanical polishing aqueous dispersion according to the present invention.

  According to the chemical mechanical polishing aqueous dispersion, an object to be processed provided with a wiring layer containing tungsten, particularly an object to be processed in which the tungsten film and an insulating film such as a silicon oxide film of the object to be processed coexist. The surface can be polished at a high polishing rate so as to be highly flat by suppressing erosion and the like, and while suppressing defects such as corrosion of the tungsten film surface.

It is sectional drawing which shows typically an example of the to-be-processed object grind | polished by the chemical mechanical polishing method which concerns on this embodiment. It is sectional drawing which shows typically the said to-be-processed object at the time of completion | finish of a 1st grinding | polishing processing process. It is sectional drawing which shows typically the said to-be-processed object at the time of completion | finish of a 2nd grinding | polishing processing process. It is a figure which shows a chemical mechanical polishing apparatus typically.

Hereinafter, preferred embodiments of the present invention will be described in detail.
1. Chemical mechanical polishing aqueous dispersion The chemical mechanical polishing aqueous dispersion according to the present invention is a chemical mechanical polishing aqueous dispersion for polishing a target object provided with a wiring layer containing tungsten. It contains (A) polyethyleneimine, (B) persulfate, and (C) colloidal silica, and the content (M _A ) of (A) polyethyleneimine is 0.002 to 0.28% by mass. The pH value is 1-3.

  The polishing target of the chemical mechanical polishing aqueous dispersion is an object to be processed such as a semiconductor wafer provided with a wiring layer containing tungsten. Specifically, an object to be processed including an insulating film (eg, silicon oxide film) having a tungsten plug can be given.

By using the chemical mechanical polishing aqueous dispersion according to the present invention, the surface to be polished on which the tungsten film and the insulating film such as the silicon oxide film coexist can be suppressed at a high polishing rate, erosion, etc. Polishing can be performed without causing defects such as corrosion.
Each component constituting the chemical mechanical polishing aqueous dispersion according to the present invention will be described below.

1.1 (A) Polyethyleneimine The chemical mechanical polishing aqueous dispersion according to the present invention contains polyethyleneimine , which is a cationic polymer compound.

  Generally, a cationic polymer compound is easily adsorbed on the surface of a tungsten film having a negative charge in an aqueous solution. As a result, since the tungsten film can be prevented from being oxidized, the chemical polishing rate of the tungsten film is suppressed. Moreover, it is thought that corrosion of the tungsten film surface generated by oxidation of the tungsten film surface is suppressed. Furthermore, according to Patent Document 3, it is considered that the cationic polymer compound also acts as a protective film against mechanical polishing.

  Polyethyleneimine is a polymer compound having the highest cation density among the generally available cationic water-soluble polymer compounds, so it adsorbs to the tungsten film surface very efficiently and exhibits the above performance remarkably. Conceivable.

  The content ratio of polyethyleneimine is 0.002% by mass to 0.28% by mass, preferably 0.004% by mass to 0.23% by mass, with respect to the total mass of the chemical mechanical polishing aqueous dispersion. Yes, and more preferably 0.008% by mass to 0.15% by mass. By using the chemical mechanical polishing aqueous dispersion in which the polyethyleneimine content is in the above range, the object to be treated can be polished while suppressing the occurrence of dishing or erosion. On the other hand, if the polyethyleneimine content is less than the above range, the effect of forming a protective film on the surface of the tungsten film is small, so the polishing speed of the tungsten film increases, and the tungsten portion is excessively polished and dishing is performed. And erosion may occur easily. In addition, corrosion of the tungsten film surface is likely to occur. If the polyethyleneimine content is higher than the above range, the polishing rate of the tungsten film is excessively suppressed, and the tungsten portion may remain without being polished.

  The number average molecular weight of polyethyleneimine is preferably 200 to 1,000,000, more preferably 10,000 to 100,000. The chemical mechanical polishing aqueous dispersion having a number average molecular weight in the above range is excellent in stability, and when the target object is polished using the chemical mechanical polishing aqueous dispersion, the polishing rate for the tungsten film is increased. And corrosion of the tungsten film surface can be suppressed.

  The number average molecular weight is a pullulan conversion value, gel permeation chromatography (column model number “Shodex Asahipak GF-710HQ + GF-510HQ + GF-310HQ” (manufactured by Showa Denko KK), and the eluent is “0.2M monoethanol. It is a value when measured with an amine aqueous solution ").

1.2 (B) Persulfate The chemical mechanical polishing aqueous dispersion according to the invention contains a persulfate. Persulfate oxidizes the surface of the tungsten film and promotes polishing of the tungsten film.

Examples of the persulfate include ammonium persulfate, potassium persulfate, and sodium persulfate. Of these persulfates, ammonium persulfate ((NH ₄ ) ₂ S ₂ O ₈ ) is particularly preferred. When the object to be treated is polished using the chemical mechanical polishing aqueous dispersion in which the persulfate is ammonium persulfate, an oxide film is formed on the surface of the tungsten film, and the oxide film is formed using colloidal silica described later. The surface to be polished can be obtained having flatness while maintaining a good polishing rate while suppressing residue, dishing and erosion. Said persulfate can be used individually by 1 type or in combination of 2 or more types.

  The content of persulfate is preferably 0.5% by mass to 3.3% by mass, more preferably 1.0% by mass to 2.5% by mass with respect to the total mass of the chemical mechanical polishing aqueous dispersion. % By mass. Polishing the object to be processed using the chemical mechanical polishing aqueous dispersion having a persulfate content in the above range can moderately promote polishing of the tungsten film while suppressing dishing and erosion. .

1.3 (C) Colloidal silica The aqueous dispersion for chemical mechanical polishing according to the present invention contains colloidal silica. Colloidal silica has the effect of mechanically polishing the tungsten film. As the colloidal silica, one produced by a known method as described in, for example, JP-A No. 2003-109921 can be used.

  The average particle size of the colloidal silica is preferably 10 nm to 150 nm, more preferably 10 nm to 100 nm. When the chemical mechanical polishing aqueous dispersion in which the average particle size of colloidal silica is within the above range is used, the target object (pattern wafer or the like) can be polished at a high speed while suppressing erosion.

The colloidal silica can be used by mixing silicas having different average particle diameters at an arbitrary concentration.
The average particle diameter of the colloidal silica is calculated from the specific surface area measured using the BET method. For the measurement of the specific surface area, for example, a flow type specific surface area automatic measuring device “micrometrics FlowSorb II 2300 (manufactured by Shimadzu Corporation)” or the like can be used. Below, the method of calculating an average particle diameter from the specific surface area of colloidal silica is demonstrated.

Assuming that the shape of the colloidal silica is a true spherical particle, the diameter of the particle is d (nm) and the specific gravity is ρ (g / cm ³ ). The surface area A of n particles is A = nπd ² . N particles mass N becomes N = ρnπd ^3/6. The specific surface area S is represented by the surface area of all the constituent particles per unit mass of the powder. Then, the specific surface area S of n particles is S = A / N = 6 / ρd. By substituting the specific gravity ρ = 2.2 of colloidal silica into this equation and converting the unit, the following equation (1) can be derived.
Average particle diameter (nm) = 2727 / S (m ² / g) (1)

  The content of colloidal silica is preferably 1% by mass to 20% by mass, more preferably 1% by mass to 15% by mass, and particularly preferably 1% by mass with respect to the total mass of the chemical mechanical polishing aqueous dispersion. Mass% to 10 mass%. The chemical mechanical polishing aqueous dispersion having a colloidal silica content within the above range is stable without agglomeration of colloidal silica, and the chemical mechanical polishing aqueous dispersion is used to treat the object to be treated. When polished, the tungsten film and the insulating film can be polished at a sufficient polishing rate.

1.4 Other Additives The chemical mechanical polishing aqueous dispersion according to the invention may further contain an oxidizing agent other than persulfate. Examples of oxidizing agents other than persulfate include hydrogen peroxide, ferric nitrate, diammonium cerium nitrate, iron sulfate, ozone, potassium periodate, and peracetic acid. These oxidizing agents can be used alone or in combination of two or more. Of these oxidizing agents, hydrogen peroxide and ferric nitrate are particularly preferable in view of oxidizing power, compatibility with the protective film, ease of handling, and the like.

  The content of the oxidizing agent other than persulfate is preferably 0.05% by mass to 5% by mass, more preferably 0.08% by mass to 3%, based on the total mass of the chemical mechanical polishing aqueous dispersion. % By mass. When the chemical mechanical polishing aqueous dispersion in which the content of the oxidizing agent is within the above range is used, the object to be processed can be polished at a sufficient polishing rate without increasing the corrosion or dishing of the tungsten film.

1.5 Content Ratio The chemical mechanical polishing aqueous dispersion according to the present invention comprises (A) polyethyleneimine content (M _A ) [mass%] and (B) persulfate content (M _B ). [% By mass] is preferably 0.0005 ≦ M _A / M _B ≦ 0.5, more preferably 0.002 ≦ M _A / M _B ≦ 0.23, and more preferably 0.003 ≦ M _A / M. _B ≦ 0.15. When the value of M _A / M _B is in the above range, excellent balance between polishing rate of the polishing rate and the insulating film to the tungsten film, when polishing the surface so as to coexist with the tungsten film and the insulating film In addition, the occurrence of erosion or prototrusion can be suppressed.

1.6 pH
The pH of the chemical mechanical polishing aqueous dispersion according to the present invention is in the range of 1 to 3, preferably in the range of 1 to 2.5. The chemical mechanical polishing aqueous dispersion having a pH in the above range is excellent in storage stability because the precipitation and separation of colloidal silica particles are suppressed. Further, when the object to be processed in which the tungsten film and the insulating film coexist is polished using the chemical mechanical polishing aqueous dispersion, the polishing rate for the insulating film such as a silicon oxide film is significantly reduced and erosion occurs. Is suppressed, and a good surface to be polished can be obtained.

  The pH described above includes inorganic acids such as hydrochloric acid, nitric acid, sulfuric acid and phosphoric acid; organic acids such as maleic acid, malonic acid, tartaric acid and oxalic acid; alkalis such as potassium hydroxide, ammonia and tetramethylammonium hydroxide, etc. By adding to the chemical mechanical polishing aqueous dispersion, it can be adjusted within the above range.

2. Chemical mechanical polishing method The chemical mechanical polishing method according to the present invention includes a step of polishing a target object provided with a wiring layer containing tungsten using the chemical mechanical polishing aqueous dispersion, preferably And a second polishing process step in which the object to be processed is an object to be processed in which a tungsten film and an insulating film such as a silicon oxide film coexist on the surface to be polished.
Hereinafter, a chemical mechanical polishing method according to the present invention will be described in detail with reference to the drawings.

2.1 To-be-processed object FIG. 1: shows sectional drawing of an example of the to-be-processed object 100 grind | polished by the chemical mechanical polishing method which concerns on this invention.
The target object 100 can be formed through the following steps.

  (1) First, as shown in FIG. 1, a base 10 is prepared. The base 10 may be composed of, for example, a silicon substrate and a silicon oxide film formed thereon. Furthermore, a functional device such as a transistor may be formed on the substrate 10. Next, a silicon oxide film 12 that is an insulating film is formed on the substrate 10 by using a CVD method or a thermal oxidation method.

(2) Next, the silicon oxide film 12 is patterned. Using the obtained pattern as a mask, a plug 14 is formed on the silicon oxide film 12 by applying a photolithography method.
(3) Next, if necessary, sputtering is applied to form a barrier metal film 16 on the surface of the silicon oxide film 12 and the inner wall surface of the plug 14. The adhesion between the tungsten film (plug 14) and the silicon oxide film 12 is not very good, but good adhesion is obtained by interposing a barrier metal film. Examples of the material of the barrier metal film 16 include titanium and / or titanium nitride.
(4) Next, the tungsten film 18 is formed by applying the CVD method.

2.2 Chemical mechanical polishing method
2.2.1 First Polishing Process Step In the first polishing process step, an object to be processed as shown in FIG. 1 is made from a tungsten film 18 and a barrier metal film 16 provided as necessary, as shown in FIG. Is polished until the silicon oxide film 12 is exposed.

2.2.2 Second Polishing Process Step The second polishing process step is a step of simultaneously polishing the tungsten film 18, the silicon oxide film 12, and the barrier metal film 16 provided as necessary, as shown in FIG. is there. When polishing is performed using the chemical mechanical polishing aqueous dispersion according to the present invention in the second polishing processing step, the chemical mechanical polishing aqueous dispersion has non-selective polishing properties for the tungsten film and the silicon oxide film. A finished surface with extremely excellent flatness can be obtained.

2.2.3 Chemical mechanical polishing apparatus In the first polishing process and the second polishing process, for example, a chemical mechanical polishing apparatus 200 as shown in FIG. 4 can be used. FIG. 4 shows a schematic diagram of the chemical mechanical polishing apparatus 200. The slurry (chemical mechanical polishing aqueous dispersion) 44 is supplied from the slurry supply nozzle 42, and the carrier head 52 holding the semiconductor substrate 50 is brought into contact with the turntable 48 to which the polishing cloth 46 is attached. To do. In FIG. 4, the water supply nozzle 54 and the dresser 56 are also shown.

The polishing load of the carrier head 52 can be selected, for example, within a range of 10 to 1,000 hPa, and preferably 50 to 500 hPa. Moreover, the rotation speed of the turntable 48 and the carrier head 52 can be suitably selected, for example within the range of 10-400 rpm, Preferably it is 30-150 rpm. Flow rate of the slurry slurry supplied from the supply nozzle 42 (chemical mechanical polishing aqueous dispersion) 44 may be selected within the range of e.g. 10~1,000cm ³ / min, preferably 50~400cm ³ / min It is.

  As a commercially available chemical mechanical polishing apparatus, for example, “EPO-112”, “EPO-222” manufactured by Ebara Manufacturing Co., Ltd .; “LGP-510”, “LGP-552” manufactured by Lapmaster SFT, Applied Materials Product type, “Mirra”, “Reflexion” and the like.

EXAMPLES Hereinafter, although an Example demonstrates this invention, this invention is not limited at all by these Examples.
3.1 Preparation of aqueous dispersion for chemical mechanical polishing
3.1.1 Preparation of colloidal silica aqueous dispersion No. 3 water glass (silica concentration: 24% by mass) was diluted with water to obtain a diluted sodium silicate aqueous solution having a silica concentration of 3.0% by mass. This diluted sodium silicate aqueous solution was passed through a hydrogen-type cation exchange resin layer to obtain a pH 3.1 active silicic acid aqueous solution from which most of the sodium ions were removed. Thereafter, 10% by weight aqueous potassium hydroxide solution was immediately added with stirring to adjust the pH to 7.2, followed by further heating and boiling for 3 hours. To the resulting aqueous solution, 10 times the amount of the active silicic acid aqueous solution whose pH was previously adjusted to 7.2 was added little by little to grow colloidal silica.

  Next, the dispersion aqueous solution containing the colloidal silica was concentrated under reduced pressure to obtain an aqueous colloidal silica dispersion having a silica concentration of 32.0 mass% and a pH of 9.8. This colloidal silica aqueous dispersion was passed again through the hydrogen-type cation exchange resin layer to remove most of the sodium, and then added with a 10% by mass potassium hydroxide aqueous solution to obtain a silica particle concentration of 28.0% by mass, A colloidal silica aqueous dispersion having a pH of 10.0 was obtained.

  The average particle size calculated from the specific surface area measured using the BET method was 45 nm. In the measurement of the surface area of the colloidal silica particles by the BET method, the value obtained by measuring the colloidal silica recovered by concentrating and drying the silica particle dispersion was used.

  Further, colloidal silica having average particle diameters of 45 nm and 80 nm, respectively, calculated from the specific surface area measured using the BET method by the same method as above while controlling the heat aging time, the type and amount of the basic compound, etc. An aqueous dispersion was obtained.

3.1.2 Preparation of Aqueous Dispersion for Chemical Mechanical Polishing 50 parts by mass of ion-exchanged water, 5 parts by mass in terms of silica, colloidal silica aqueous dispersion having an average particle size of 45 nm, and in terms of silica 1 part by mass of an aqueous dispersion of colloidal silica having an average particle size of 80 nm is placed in a polyethylene bottle, and polyethyleneimine (trade name: P-1000, manufactured by Nippon Shokubai Co., Ltd., number average molecular weight: 16). , 000) aqueous solution was added in an amount corresponding to 0.003 parts by mass in terms of polymer amount. Next, 3 parts by mass of ammonium persulfate was added, and these were stirred for 15 minutes. Finally, maleic acid and ion-exchanged water are added so that the total amount of all components is 100 parts by mass, and then filtered with a filter having a pore size of 1 μm, whereby the chemical mechanical polishing aqueous dispersion A is obtained. Obtained.

  (A) Preparation method of said chemical mechanical polishing aqueous dispersion A except that polyethyleneimine, (B) persulfate, and (C) colloidal silica were changed to the components and content ratios shown in Tables 1 to 4 In the same manner, aqueous dispersions B to Q for chemical mechanical polishing were produced. In addition, in the chemical mechanical polishing aqueous dispersion Q, instead of polyethyleneimine, allylmethylethylammonium ethyl sulfate sulfur dioxide copolymer (trade name: PAS-2401, manufactured by Nitto Boseki Co., Ltd., number average molecular weight: 2,000) was used.

3.2 Evaluation method
3.2.1 Blanket Wafer Evaluation Method A chemical mechanical polishing apparatus (Ebara Seisakusho, model “EPO112”) is equipped with a porous polyurethane polishing pad (Nitta Haas, product number “POLITEX”). While supplying the aqueous dispersions A to Q for polishing, the following polishing rate measurement substrate was subjected to chemical mechanical polishing treatment for 1 minute under the following polishing conditions, and the polishing rate was evaluated by the following method. The results are shown in Tables 1-4.

(1) Polishing rate measuring substrate / PETOS film having a thickness of 1,000 nm provided on an 8-inch silicon substrate.
(2) Polishing conditions and head rotation speed: 80 rpm
・ Head load: 250 hPa
・ Table rotation speed: 85rpm
-Supply rate of chemical mechanical polishing aqueous dispersion: 120 ml / min

(3) Blanket wafer evaluation method The film thickness of the PETEOS film after the polishing treatment is measured using an optical interference type film thickness measuring instrument (Nanometrics Japan, model “Nano Spec 6100”), and chemical mechanical polishing is performed. The polishing rate was calculated from the reduced film thickness and polishing time.
The case where the polishing rate of the PETEOS film is 40 nm / min or more is good (◯), the case where it is 60 nm / min or more is excellent (◎), and the case where it is less than 40 nm / min is bad (×) It was evaluated.

3.2.2 Pattern wafer evaluation method A porous polyurethane polishing pad (Nitta Haas, product number "IC1000") is attached to a chemical mechanical polishing apparatus (Ebara Manufacturing, model "EPO112"). About the substrate, tungsten was removed by the first polishing process until the silicon oxide film (PETEOS film) was exposed. Thereafter, a polishing pad made of porous polyurethane (product number “POLITEX” manufactured by Nitta Haas Co., Ltd.) is attached to a chemical mechanical polishing apparatus (manufactured by Ebara Corporation, model “EPO112”), and chemical mechanical polishing aqueous dispersions A to Q are attached. Then, chemical mechanical polishing (second polishing process) was performed until the polishing amount of the silicon oxide film reached 50 nm under the following polishing conditions, and erosion was evaluated by the following method. The results are shown in Tables 1-4.

(1) Substrate QCEETC057 ((silicon oxide film) / 25 nm thick Ti film / 40 nm thick TiN film in this order, which is a substrate with a pattern, is a substrate with a pattern, and is oxidized with a pattern. (Test substrate in which a tungsten film having a thickness of 500 nm is provided on a silicon film and a tungsten plug is provided in a pattern portion)
(2) Polishing conditions and head rotation speed: 80 rpm
・ Head load: 250 hPa
・ Table rotation speed: 85rpm
-Supply rate of chemical mechanical polishing aqueous dispersion: 120 ml / min

(3) Erosion Evaluation Method For the surface to be polished after polishing, a plug pattern part (hole diameter: 0.3 μm, coverage: 4%) using a high resolution profiler (model KRP Tencor), model “HRP240ETCH” The amount of erosion (nm) was measured. The results are listed in Tables 1 to 4. Note that the erosion amount is indicated as minus when the plug pattern portion is convex above the reference surface (the upper surface of the insulating film (silicon oxide film)). When the amount of erosion was −10 to 20 nm, it was evaluated as good (◯), and when it was −5 to 15 nm within this range, it was excellent (◎), and when it was outside this range, it was poor (×) It was evaluated.

(4) Evaluation Method of Tungsten Film Surface Corrosion For the surface to be polished after polishing, using a SEM (manufactured by Hitachi High-Tech, model “S4800”), in the plug pattern portion (hole diameter 0.3 μm, coverage 4%) The presence or absence of corrosion was measured. The results are listed in Tables 1 to 4.

3.2.3 Evaluation Method of Storage Stability The chemical mechanical polishing aqueous dispersions A to Q are stored in a sealed thermostat at 25 ° C. for 3 months, and the presence or absence of precipitates and the presence or absence of agglomeration / separation. investigated. The results are listed in Tables 1 to 4.

3.3 Evaluation results

実施例１〜１２の化学機械研磨用水系分散体を用いた場合には、いずれも、ＰＥＴＥＯＳ膜の研磨において高い研磨速度が達成され、またパターン付き研磨基板の研磨において、エロージョンの発生を抑制でき、かつ腐食の抑制された研磨面を得ることができた。

When the chemical mechanical polishing aqueous dispersions of Examples 1 to 12 were used, a high polishing rate was achieved in polishing the PETEOS film, and generation of erosion could be suppressed in polishing the patterned polishing substrate. In addition, it was possible to obtain a polished surface in which corrosion was suppressed.

In the chemical mechanical polishing aqueous dispersion of Comparative Example 1, the polyethyleneimine content (M _A ) was less than 0.002 mass%. Therefore, the erosion was clearly worsened.
In the chemical mechanical polishing aqueous dispersion of Comparative Example 2, the polyethyleneimine content (M _A ) exceeded 0.28 mass%. Therefore, protolution occurred.

  The chemical mechanical polishing aqueous dispersion of Comparative Example 3 had a pH exceeding 3. Therefore, colloidal silica particles were precipitated and separated, and the storage stability as an aqueous dispersion for chemical mechanical polishing deteriorated.

The chemical mechanical polishing aqueous dispersion of Comparative Example 4 did not contain colloidal silica. Therefore, a sufficient polishing rate for the silicon oxide film (PETEOS film) cannot be obtained.
In the chemical mechanical polishing aqueous dispersion of Comparative Example 5, diallylmethylethylammonium ethyl sulfate sulfur dioxide copolymer, which is a kind of polymer having a quaternary nitrogen atom listed in Patent Document 3, instead of polyethyleneimine Was used. Therefore, the erosion was clearly worsened. Corrosion of the tungsten film surface was also observed.

  The chemical mechanical polishing aqueous dispersion according to the present invention includes Cu, Al, W, Ti, TiN, Ta, TaN, V, Mo, Ru, Zr, Mn, Ni, Fe, Ag, Mg, Mn, or Si. It is expected to be effective for a layered structure including a layer composed of the above and a layer composed of these elements or compounds.

DESCRIPTION OF SYMBOLS 10 ... Base | substrate 12 ... Silicon oxide film 14 ... Plug 16 ... Barrier metal film 18 ... Tungsten film 42 ... Slurry supply nozzle 44 ... Slurry 46 ... Polishing cloth 48 ... Turntable 50 ... Semiconductor substrate 52 ... Carrier head 54 ... Water supply nozzle 56 ... Dresser 100 ... Subject 200 ... Chemical mechanical polishing apparatus

Claims (8)

An aqueous dispersion for chemical mechanical polishing for polishing an object to be processed provided with a wiring layer containing tungsten,
(A) polyethyleneimine;
(B) persulfate;
(C) containing colloidal silica,
The content ratio (M _A ) of (A) polyethyleneimine is 0.002 to 0.28% by mass,
A chemical mechanical polishing aqueous dispersion having a pH value of 1 to 3.   The aqueous dispersion for chemical mechanical polishing according to claim 1, wherein the (B) persulfate is ammonium persulfate.   3. The chemical mechanical polishing aqueous dispersion according to claim 1, wherein the (A) polyethyleneimine has a number average molecular weight of 200 to 1,000,000. 4. (B) the content of the persulfate (M _B) is 0.5 wt% to 3.3 wt%, the chemical mechanical polishing aqueous dispersion according to any one of claims 1 to 3 body. 5. The chemical mechanical polishing aqueous dispersion according to claim 1, wherein the content ratio (M _C ) of the (C) colloidal silica is 1% by mass to 20% by mass.   The chemical mechanical polishing aqueous dispersion according to any one of claims 1 to 5, wherein the object to be processed includes an insulating film having a tungsten plug. (A) the content of polyethyleneimine (M _A) [wt%] and the (B) content of the persulfate (M _B) [wt%] _{is, 0.0005 ≦ M A / M B} ≦ 0. The chemical mechanical polishing aqueous dispersion according to any one of claims 1 to 6, which has a relationship of 5.   A chemical mechanical polishing method for polishing a target object provided with a wiring layer containing tungsten using the chemical mechanical polishing aqueous dispersion according to claim 1.

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